With the proliferation of smartphones and tablet terminals, capacitive touch panels have recently been receiving attention. Sensor substrates for capacitive touch panels typically have wiring in which indium tin oxide (ITO) or metal (e.g., silver, molybdenum, or aluminum) is patterned on a glass, insulating films at intersections of wires, and a protecting film to protect ITO and metal. Typically, protecting films are formed from a high-hardness inorganic compound SiO2 or SiNx, photosensitive clear materials, or the like (Patent Document 1), and insulating films are formed from photosensitive clear materials. Inorganic materials, however, have a problem of high production cost: for example, the film is formed at a high temperature by chemical vapor deposition (CVD) of SiO2 or SiNx, and in addition, an increased number of processes is required because patterning using resists is performed. For photosensitive clear materials, production cost can be reduced because of a decreased number of processes, but there is a problem of poor hardness and a chemical resistance insufficient to withstand a mass production process. Further, the photosensitive clear materials are also used for insulating films, but they have a problem in that outgas generates during a subsequent ITO-forming process, increasing the resistance of ITO. Such being the situation, photosensitive clear materials are now demanded that have high hardness, is excellent in transparency, heat resistance, and chemical resistance, and further can be patterned.
Known photosensitive clear materials include UV-crosslinking coating compositions containing an alkali-soluble polymer, a monomer, a photo-polymerization initiator, and other additives. The UV-crosslinking coating compositions are used, for example, as overcoat materials or spacer materials for color filters, and also used for color resists when further containing a coloring agent (Patent Documents 2 and 3). Furthermore, the UV-crosslinking coating compositions are used in wide applications such as interlayer dielectric film formation and solder resists (Patent Documents 4 and 5).
Multifunctional epoxy compounds are known to contribute to improvement of the properties of the UV-crosslinking coating compositions as described above, more specifically, improvement of chemical resistance (Patent Document 3), improvement of heat resistance (Patent Document 4), and improvement of photosensitivity (Patent Document 5).